New Hope for Endangered Mountain Yellow-Legged Frog



A critically endangered mountain yellow-legged frog/Credit Adam Backlin, USGS

Good news in the conservation world is always welcome. First, I wrote about the discovery of a brand new all-black tink frog in Costa Rica. Now, I’ve learned that biologists rediscovered a population of critically endangered mountain yellow legged frogs (Rana muscosa) – not seen here in over 50 years – in California’s San Bernadino National Forest’s San Jacinto Wilderness area. Before this discovery, biologists estimated a mere 122 frogs remained in the wild.

In June, Adam Backlin and Liz Gallegos of the U.S. Geological Survey were surveying the remote region to figure out whether it would serve as a good locale to reintroduce the species. While surveying Tahquitz Creek, which had served as a good habitat for the frogs in times past, they got a welcome surprise. “We wanted to evaluate the site for perennial water, invasive species like predatory fish, and stream structure,” says Backlin. “If the site appeared suitable, we were intending to release tadpoles from our captive population as soon as next year. To our surprise we found a large female adult mountain yellow-legged frog!”

Backlin says the discovery changed the plans for the creek region. Scientists at the San Diego Zoo’s Institute for Conservation Research had just successfully bred the frogs in captivity, which is a feat in itself since frogs tend to be more challenging when it comes to captive breeding. Instead of introducing tadpoles bred from captivity at the creek, now they need to extensively survey the site and figure out just how many frogs live there. Though Gallegos and Backlin only found the one female in their three days of surveying after finding her on June 10th, scientists from the San Diego Natural History Museum found a second frog about two and a half miles away on June 25th, suggesting the frog population could be large, extending over that range. Eight other tiny populations exist of the frogs, each comprising only a half-mile of stream.

Recovery efforts for the frog were funded partly by Caltrans, the California Department of Transportation, to mitigate the effects of emergency work done on state route 330 to stabilize a mountain slope near the frog’s known habitat.  Biologists with the California Department of Fish & Game (DFG) have been working to remove stocked, non-native rainbow trout from Little Rock Creek since 2002, one of the river drainages that has the frogs, to help boost their numbers. The trout think the tadpoles are yummy.

Tim Hovey, DFG biologist says they increased their trout removal efforts in 2008 and they've seen a marked difference. "When we started there were 11 adults upstream of our removal reach. A count of frogs this year placed the number at 80 plus," says Hovey. "We believe that with these increase removal efforts we may be able to complete remove all the trout in the removal reach, giving the mountain yellow-legged frog some room to extend its range and habitat downstream."

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